Fuel injection valve

ABSTRACT

In a fuel injection valve for slanted fuel injection, provided between a conical flow path and an injection port is an intermediate flow path having a cylindrical surface coaxial to the conical flow path, so that the injection port has a portion of the cylindrical surface connected to the conical surface of the conical flow path and another portion of the cylindrical surface connected to the cylindrical surface of the intermediate flow path, whereby generation of stagnation of flow of fuel is suppressed to decrease the formation of the carbon deposit. The intermediate flow path has a tapered conical surface that is connected to a downstream side end portion of said cylindrical surface and that includes a diameter gradually decreases in the direction of flow of fuel to cope with where the injection port diameter is small. A cone apex angle of the conical surface of the intermediate flow path is smaller than a cone apex angle of the valve seat surface.

TECHNICAL FIELD

This invention relates to a fuel injection valve and particularly to afuel injection valve for an internal combustion engine in which the fuelinjection port is slanted with respect to the central axis.

BACKGROUND ART

The conventional fuel injection valve to which the present inventionconcerns comprises a valve seat, a valve member aligned with the valveseat and capable of engaging and separating therefrom, and an actuatorfor actuating the valve member. The valve seat includes a valve seatsurface defining a conical flow path having a conical surface that has adiameter decreasing in the direction of flow of the fuel, and aninjection port having a cylindrical surface communicating with theconical flow path at its downstream side. The valve member has asubstantially conical tip and capable of contacting to and separatingfrom the valve seat surface to control the supply of fuel to theinjection port. The injection port is slanted with respect to thecentral axis of the conical flow path in order to efficiently utilizethe energy of the swirling fuel due to a swirler in atomizing the fuel.(See Japanese Patent Laid-Open No. 10-184496, for example)

However, in the fuel injection valve that has a fuel injection portslanted with respect to the valve central axis as above described, theangle defined between the conical surface and the cylindrical surface issmall to exhibit an acute angle on a side close to the slanted surfaceand is large at the other side. Therefore, the fuel that flows along theconical surface looses its flow speed at the downstream of such theacute angle to generate a stagnation, resulting in a cause of a depositof carbon contained in the fuel on the fuel flow path wall surfacecorresponding to the stagnation. The stagnation easily generates whenthe slant angle of the injection port with respect to the central axisof the fuel injection valve is large.

Accordingly, the object of the present invention is to provide a fuelinjection valve in which the amount of carbon deposit is small.

DISCLOSURE OF INVENTION

With the above object in view, the fuel injection valve of the presentinvention comprises a valve seat including an injection port having avalve seat surface defining a conical flow path including a conicalsurface that gradually decreases in diameter in the direction of flow offuel, and a cylindrical surface including a central axis slanted withrespect to the central axis of the conical flow path, a valve memberhaving a substantially conical tip for contacting and separating withrespect to the valve seat surface to control supply of fuel into theinjection port, and an actuator for actuating the valve member, the fuelinjection valve being characterized in that an intermediate flow pathhaving a cylindrical surface coaxial to the conical flow path isprovided between the conical flow path and the injection port, and thatthe injection port has a portion of the cylindrical surface connected tothe conical surface of the conical flow path and another portion of thecylindrical surface connected to the cylindrical surface of theintermediate flow path, whereby generation of stagnation of flow of fuelis suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of the fuel injection valve ofthe present invention.

FIG. 2 is an enlarged view showing the fuel flow path between the valvemember and the valve seat according to an embodiment of the fuelinjection valve of the present invention.

FIG. 3 is an enlarged view showing the fuel flow path according toanother embodiment of the fuel injection valve of the present invention.

FIG. 4 is an enlarged view for explaining the structure of the fuelinjection valve shown in FIG. 3.

FIG. 5 is an enlarged view showing the fuel flow path when the diameterof the injection port of the fuel injection valve shown in FIGS. 3 and 4is small.

BEST MODE FOR CARRYING OUT THE INVENTION

As illustrated in FIG. 1, a fuel injection valve 1 of the presentinvention comprises a solenoid unit 2, and the solenoid unit 2 comprisesa housing 3 which is also a yoke portion of a magnetic circuit, a core 4which is a stationary core portion of the magnetic core, a coil 5, anarmature 6 which is a movable core portion slidably held by a holderportion 14 of the housing 3, and a spring 13 for biasing the armature 6.The solenoid unit 2 has connected thereto a valve unit 7 to achieve theopen and close operation of the valve unit 7, so that the solenoid unit2 is an actuator. The valve unit 7 comprises a valve member 8 connectedto the armature 6, a valve main body 9 connected to the housing 3 viathe holder portion 14, a swirler 10 disposed within the valve main body9 for providing the fuel flow with a swirling motion, a valve seat 11for controlling the flow of the fuel, and a stopper 12 for restrictingthe movement of the valve member 8.

When an electric current flows through the coil 5 of the fuel injectionvalve, a magnetic flux is generated in a magnetic circuit composed ofthe armature 6, the core 4 and the housing (yoke) 3 to cause thearmature 6 to be attracted toward the core 4, whereby the valve member 8integral to the armature 6 separates from the valve seat 11 to form aclearance therebetween. Then, a high pressure fuel (pressure of 3 MPa)is injected from the injection port 15 into the engine cylinder (notillustrated) and is burned after a few milliseconds. At this time, thefuel injected from the injection port 15 is given a swirling motionenergy by the swirler 10 disposed upstream of the valve seat 11 andbecomes a spiral flow in the injection port 15 and then injected as acone-shaped spray into the engine cylinder. When the current supply tothe coil 5 is stopped, the magnetic flux in the magnetic circuitdecreases to close the clearance between the valve member 8 and thevalve seat 11 because of the compression spring 13, terminating the fuelinjection. The valve member 8 slides within the valve main body 9 and,in the valve open state, stops with the flange 8 a brought into abutmentwith the stopper 12

FIG. 2 is an enlarged view showing the fuel flow path between the valvemember and the valve seat of the fuel injection valve shown in FIG. 1,in which the state of the valve member 8 being in an open valve positionseparated from the valve seat 11 is illustrated. The valve seat 11 isprovided with a valve seat surface 17 defining a conical flow path 16including a conical surface having a diameter that gradually decreasesin the direction of fuel flow, and the injection port 15 connected atthe downstream side of the conical flow path 16 is provided with acylindrical surface 20 having a central axis 19 slanted with respect tothe central axis 18 of the conical flow path 16. The valve member 8 hasa substantially cone-shaped tip and is brought into a contacting andseparating relationship with respect to the valve seat surface 17 tocontrol the supply of the fuel into the injection port 15.

The valve seat 11 further comprises an intermediate flow path 22 havinga cylindrical surface 21 coaxial to the conical flow path 16 between theconical flow path 16 and the injection port 15 (that is, the centralaxis of the intermediate flow path 22 coincides with the central axis 18of the conical flow path 16). Since the diameter of the intermediateflow path 22 is substantially equal to that of the injection port 15,the intermediate flow path 22 appears only partially between the conicalflow path 16 and the injection port 15, and the cylindrical surface 20of the injection port 15 has one portion (the portion on the side wherethe change in the angle relative to the valve seat surface 17 is small)connected to the valve seat surface 17 which is the conical surface ofthe conical flow path 16 and has another portion (the portion on theside where the change in the angle relative to the valve seat surface 17is large) connected to the cylindrical surface 21 of the intermediateflow path 22. Therefore, the resulted configuration is such that thatportion where the change in the angle between the valve seat surface 17and the cylindrical surface 20 of the injection port 15 is large is cutoff.

According to such arrangement, the flow of the fuel at this portion ismade smooth to reduce the loss and to suppress the stagnation, so thatthe accumulation of the carbon deposit 23 is small as illustrated. Thecircumference on the upstream side of the injection port 15 is connectedat one portion to the intermediate flow path 22 and at a still anotherportion to the valve seat surface 17, so that the number of the portionsat which the fuel flow direction changes is small as compared to thatwhere entire circumference on the upstream side of the injection port 15is connected to the intermediate flow path 22 and where the flow path isbent. It is to be noted that the particularly advantageous results dueto the intermediate flow path 22 can be obtained when the slant angle ofthe injection ports is large, such as 30 degrees or more.

FIG. 3 is an enlarged view showing the fuel flow path in anotherembodiment of the fuel injection valve of the present invention. In thisfuel injection valve, as best seen from FIG. 4, the intermediate flowpath 24 has a tapered conical surface 25 that is connected to thedownstream side end portion of the cylindrical surface 21 and that has adiameter gradually decreases in the direction of flow of the fuel, andthe conical surface 25 has one portion of the circumference of the upperend of the cylindrical surface 20 of the injection port 15 previouslydescribed. The apex angle B of the conical surface 25 of theintermediate flow path 24 is made smaller than the apex angle A of theconical surface of the valve seat surface 17 (B<A). Thus, the upper endof the injection port 15 is connected to the valve seat surface 17 whichis the conical surface of the conical flow path 16, a cylindricalsurface 21 of the intermediate flow path 24 and the conical surface 25of the intermediate flow path 24 and has a configuration that has nosignificant angle change between the valve seat surface 17 and theinjection port 15. Therefore, it is difficult for the carbon deposit 23that may be formed on the flow path walls to deposits and, even whendeposited, the amount may be small.

In this fuel injection valve, the inner diameter of the injection port15 is small as compared to that of the fuel injection valve illustratedin FIG. 2, and it is prevented that the lower end portion of theintermediate flow path 24 which is the cylindrical flow path cuts intothe cylindrical surface 20 of the injection port 15 and forms a dimple26 therein as shown in FIG. 5.

The advantageous effect obtained by the use of the fuel injection valveof the present invention in an internal combustion engine is that, evenwhen a large slant angle is given to the direction of the fuel injectionwith respect to the direction of installation of the fuel injectionvalve, the decrease in amount of fuel injection due to the carbondeposit and the deterioration in atomization of the injected fuel can beminimized, so that the initial engine performance of the new engine canbe maintained even after a long time use.

1. A fuel injection valve comprising; a valve seat comprising a valveseat surface defining a conical flow path including a conical surfacethat gradually decreases in diameter in the direction of flow of fuel,and an injection port with a cylindrical surface including a centralaxis slanted with respect to the central axis of said conical flow path;a valve member having a substantially conical tip for contacting andseparating with respect to said valve seat surface to control supply offuel into said injection port; and an actuator for actuating said valvemember, wherein, an intermediate flow path having a cylindrical surfacecoaxial to said conical flow path is provided between said conical flowpath and said injection port; and a portion of said cylindrical surfaceof said injection port is connected to said conical surface of saidconical flow path and another portion of said cylindrical surface ofsaid injection port is connected to said cylindrical surface of saidintermediate flow path; whereby generation of stagnation of flow of fuelis suppressed.
 2. A fuel injection valve as claimed in claim 1, whereinsaid intermediate flow path has a tapered conical surface that isconnected to a downstream side end portion of said cylindrical surfaceof said intermediate flow path and that includes a diameter whichgradually decreases in the direction of flow of fuel, and wherein astill another portion of said cylindrical surface of said injection portis connected to said tapered conical surface of said intermediate flowpath.
 3. A fuel injection valve as claimed in claim 2, wherein a coneapex angle of said conical surface of said intermediate flow path issmaller than a cone apex angle of said valve seat surface.